A lid for a beverage can has a curled portion thereof and a flange portion of a can body that is filled with contents mated and joined with pressure bonding by a seaming apparatus called “seamer”. The beverage can manufactured in such a manner is required to have a predetermined pressure resistant strength. The predetermined pressure resistant strength can be ensured by increasing the thickness of can lid and can body, but from the standpoint of cost reduction and environmental protection, a technology is required that makes it possible to reduce the thickness with the predetermined pressure resistant strength maintained. Accordingly, various can lids have been suggested which have the predetermined pressure resistant strength even if thicknesses are reduced. In particular, various full-form ends in which pressure resistant strength is increased by improving the outer side shape of a center panel portion have been suggested.
One of them is a can lid having a reinforced annular groove portion provided with a plurality of annular grooves, rather than a single annular groove, in which the annular grooves are tilted radially inward (for example, see FIG. 4 of Patent Document 1).
A can lid is also known in which an annular groove is eliminated by folding the outer side of a center panel portion radially inward (for example, see Patent Document 2).
Thus, because the cross-sectional shape of the outer side of a center panel portion greatly affects the pressure resistant strength of cans, various can lids have been suggested that have specific features in the cross-sectional shape thereof in addition to the above.    Patent Document 1: Japanese Patent Application Laid-open No. 2005-119747.    Patent Document 2: Japanese Patent Application Laid-open No. H7-76344.